This invention relates generally to inner tubes for tires. More particularly this invention relates to a pneumatically-inflated inner tube that has two compartments such that if one compartment is damaged and deflates, the other compartment may be inflated without removing the tire. Each compartment has its own valve for inflation.
As known in prior art, an inner tube is typically an annular sheath of thin rubber-like material which, when filled with air and inserted in a tire casing, becomes a firm support for the flexible tire casing. The tire and inner tube assembly is then attached to a wheel for use on a bicycle, motorcycle or automobile. Inner tubes are thin-walled to achieve flexibility and elasticity and to reduce cost of manufacture and total weight of the tire assembly. However, because the tube walls are so thin, they are easily damaged. Once damaged, an inner tube will deflate and the tire will lose its support and go flat. In order to continue using the tire, the tire must then be removed from the wheel, the inner tube removed, repaired and replaced into the tire casing, and the whole tire assembly replaced on the wheel.
Removing, repairing and replacing an inner tube is time consuming. For bicycle and motorcycle racing, time is of the essence and the minutes spent changing a tire that has gone flat because of damage to its inner tube can be the difference between winning and losing the race. To combat losing this time, bicycle racers often carry spare inner tubes with them around their necks or waists. When a tire goes flat, a racer will stop and remove the tire from the wheel, remove the inner tube and either repair or replace it, and then reassemble the tire and wheel. Others racers have crews in vans or trucks with spare tires and tubes who follow along the bicycle route in case of a flat. If using the crews the racer does not have to carry his own supplies, but the time necessary to fix the flat is about the same. However, for mountain bike riders, these means of preparation are impractical.
Mountain bike trails often lead into rough terrain where the only means of access is by bike or on foot. The ground is rocky and cluttered with sharp stones, sticks and cactus spines. When a tire goes flat because the tube has been damaged, the options are limited to walking out (sometimes carrying the bike) or replacing the tube at the site it went flat. Because of the relative inaccessibility of mountain bike trails, the equipment and materials necessary to repair a flat on the trail must be carried along with the rider, adding weight and making the ride more strenuous. Both walking out and repairing a flat tire on a trail take considerable time and effort. If the flat occurs during a race, the race can be lost. But even if only on a recreational bike ride, the replacement of a tube can be frustrating and can ruin the ride by ending it prematurely.
By providing an inner tube with two compartments, a flat tire can be repaired quickly on the trail with little effort and little extra equipment. By employing the present invention, a second compartment within the existing inner tube acts like a spare inner tube. When the tire goes flat because the inner tube has been punctured, the rider simply inflates the second compartment already residing in the tire by using a standard air pump carried on the frame of the bicycle or by using a pressurized cartridge of CO.sub.2. The tire does not have to be removed from the wheel in order to fix the flat. Time is saved and little effort is used to inflate the "spare" tube which is already in place.
Prior attempts have been made to solve the problem of repairing a damaged inner tube without removing the tire. U.S. Pat. No. 5,099,900 describes a self-healing tire system having an inner tube that is coated with a tacky sealant material. If the tube is punctured, the sealant material flows around and over the puncture site to seal it and prevent pressurized air from escaping. However, if the damage to the tube is too severe, the tacky sealant will not be able to seal the hole and the tube will have to be removed for repair or replacement.
Another U.S. Pat. No. 4,143,697, describes an inner tube assembly that has two annular chambers that are interconnected by one valve and separated by a retaining band. When the outermost chamber deflates, the innermost chamber maintains its pressure. However, the innermost chamber is necessarily of smaller diameter than the outermost chamber and if the outermost chamber deflates, the innermost chamber is limited in its circumferential expansion by the retaining band and consequently the tire volume is not completely supported.